The present invention relates to an electronic focusing position detection apparatus for detecting a focusing position in cameras and the like.
Conventionally, there is known a focusing position detection apparatus utilizing a photoelectric element whose resistance becomes maximum when the image of an object is focused on the photoelectric element. In another conventional focusing position detection apparatus, double images of the object are respectively projected onto different photoelectric elements and the difference between the electric currents which flow through the respective photoelectric element is measured and when the image of the object is focused, the difference of the photoelectric currents becomes minimum.
In these focusing position detection apparatuses, the focusing position itself can be determined. However, when the object is out of focus, it cannot be determined whether the focused position is in front of the film surface (hereafter referred to as a front focusing state) or the focused position is behind the film surface (referred to as a back focusing state). Therefore, in these apparatuses, it is required that a prescanning be initiated from a predetermined direction, for example, from close range to infinite range so that the focusing position is searched and detected and then the photographing lens is moved to the detected focusing position. This prescanning step, however, is laborious.
Furthermore, in this type of the focusing position detection apparatuses a lenticular lens group consisting of a number of small lens elements is used and the small lens elements are adjacent each other and are made integrally, and near the boundary areas of a convex surface of each small lens element, each lens element has a radius of curvature which is different from a predetermined radius of curvature or has a reversed radius of curvature in a certain range. Therefore, although all the rays of light which enter one small lens element have to enter its counterpart photoelectric element, some of the rays of light are refracted in the boundary areas in different directions and enter the other photoelectric elements, so that noises are produced in the output signals from the photoelectric elements. As a result, the exact focusing position cannot be detected.